Process for expanding preheated tubular bodies



A. ZIMPEL Dec. 27, 1955 PROCESS FOR EXPANDING PREHEATED TUBULAR BODIES Filed July 22, 1952 Inventor? United States Patent 2,728,373 PROCESS FOR EXPANDING PREHEATED TUBULAR BDDIES Adolf Zimpel, Dnsseldorf-Reisholz, Germany, assignor to Stahlund Rohrenwerk Reisholz Gesellschaft mit Beschraenkter Haftung Application July 22, 1952, Serial No. 300,270 Claims priority, application Germany August 4, 1951 1 Claim. (Cl. 15380.5)

This invention relates to a process and a device for expanding preheated tubular bodies and particularly metal tubes by means of plugs or mandrels.

In conformity with the art, the tubes to be expanded are preheated in a furnace; the preheated tubes are then expanded at the one end and provided with a flanged rim. The flanged rim serves as a means to grip or hold the tubes during the forced entrance and passage of a plug or mandrel. Since a tube or similar hollow body possesses a relatively large surface compared with its cross-section, it cools quickly; treatment of the tubes which requires a succession of expansion steps by means of a plurality of plugs of the increasing diameter, cannot be performed in one heat. As a consequence thereof, a series of consecutive heating steps are applied which means a large consumption of time and money. An additional disadvantage arises insofar as the preliminary widening and edging of the tubes means considerable work and material losses, which particularly applies to short tubes.

It is the main object of the invention to eliminate this drawback and to avoid the cooling of the tubes by the use of a constant heat supply during the entire expansion.

In this manner any desired number of successive repetitions of the tube expansion may be performed and a maximum expansion effect attained without incurrence of a cooling of the tubes. Any external heating source may be used for the supply of the heat and the prevention of cooling, since the tubes are expanded from the inside; therefore no obstacle exists for the application of an external heat supply.

It is particularly advisable to leave the tube during the expansion in the preheating furnace.

Prior to the entry of the expanding mandrel or plug, the tubes are pushed with their one end in a self-closing tongue, which grasps the tube end and holds it tight during the entire expansion; these holding tongues are equipped to give way during the forced entrance of the widening plug. In this manner, the heretofore customary preliminary expanding and bordering or edging treatment of the tube end prior to the introduction of the expansion plug is avoided.

The invention will now be described more in detail with reference to the accompanying drawing showing a preferred embodiment thereof. In the drawings,

Fig. l is a vertical sectional view of the tube expanding device and of the tube preheating furnace;

Fig. 2 is an enlarged vertical sectional view similar to that of Fig. 1 of the front end of the tube and of the tube holder at the commencement of the expansion;

Fig. 3 is a view similar to that of Fig. 2 in a progressed state of the work and after the insertion of an expansion plug into the front end of the tube;

Fig. 4 is a horizontal sectional view on line 44 of Fig. 3.

As apparent from the drawing, the expansion of the tube 3 is performed in a preheating furnace 2 shown in Figure 1. The tubes 3 are entered into the furnace through an opening in the direction of arrow s and are conducted through the furnace in an upward direction. The expanded tube 3a is discharged through opening 1a in the direction of arrow s As soon as the tube 3 has reached opening 4 of the 2,728,373 Patented Dec. 27, 1955 furnace wall it is pushed through the opening 4 and gripped by holder 5. This holder is provided with tongs 7 and these tongs carry jaws 8 adapted to enter the tube 3, as apparent from Figure 2. The holder 5, see Figure 1, is supported by the outer wall of the furnace 2 said wall surrounding opening 4. Plug 6 is fastened on the bolt shaped end of rod 11 by a screw 12. The rod 11 is connected to a chain 13, Figure 1, which cooperates with a sprocket wheel provided with a drive mechanism, not shown. Upon operation of this drive mechanism the plug 6 is pulled through the tube 3. The tongs 7 are fastened to guides 9 which enable a displacement of the tongs against the action of spring 10 during the entrance of plug 6, see also Fig. 3

The axes of the guides 9 are inclined in such a manner, that they extend in a substantially vertical direction; however, the inclination is so chosen that the guides 9 remain self-locking in spite of the pull exerted by the expansion of the tube to thereby prevent an unintentional divergence of the jaws 8.

These fiat jaws 8, Fig. 4, which project into the end of the tube 3 are at their inside arcuated in conformity with the shape of the plug 6 in order to reduce an additional expansion of the tube caused by the jaws and to secure a friction-free sliding-in of the plug 6 along the arcuated inner faces of the jaws 8.

As apparent from the above, the tong-shaped holder 5, 7 is located in front of the opening of the furnace 2. The advantage results that the tube need only be axially ad vanced through the wall of the furnace in order to properly secure it for the expanding procedure. The tongs 7 are outwardly displaceable and this displacement is controlled by the counter pressure of the springs 10. In this manner, the tongs may radially yield in conformity with the diameter of the plug.

In order to avoid clamping and increased friction caused by the introduction of the plug 6 and the displacement of the tongs 7, the latter are fastened to the guides 9 having their axes inclined in a substantially vertical direction.

It will be apparent to those skilled in the art that the novel principles of the invention disclosed herein in connection with specific exemplifications thereof will suggest various other modifications and applications of the same. It is accordingly desired that in construing the breadth of the appended claim it shall not be limited to the specific exemplifications of the invention described herein.

Having thus described the invention, what I claim as new and desire to be secured by Letters Patent, is as follows:

The method of expanding metal tubes comprising conducting said tubes through the inner space of a heated furnace, pushing an end portion of said tube through an opening of the furnace wall into a self-closing tong-shaped holder adapted to tightly grip said tube, forcing an expansion plug into the gripped tube end and thereafter through the entire tube and removing the widened tube from said furnace.

References Cited in the file of this patent UNITED STATES PATENTS 

